This invention relates in general to cutting tools and more particularly to rotary slot cutting tools.
Such rotary tools are used to cut slots in solid materials, especially metals, or to separate the solid materials by cutting through the material. These rotary tools comprise discs with centrally keyed mounting apertures and having peripherally disposed cutting elements. The cutting elements, within the scope of the invention, can be integral to the discs, can be fixedly attached to the discs such as by brazing, or can be removably attached to the discs generally by clamping means. Generally, because of the shearing and centrifugal forces, relatively complicated clamping arrangements have been used for retaining the cutting inserts in seats on the discs. Such clamping arrangements besides being costly and time consuming limit the number of inserts on the disc.
The continuous disposal of the chips generated during the cutting operation is a problem that is present in all cutting operations. However the problem is compounded by the use of rotary cutting tools having a plurality of sequential cutting elements, since, for example, in addition to the problem of presently generated chips there is the problem of the chips generated by the prior cutting element unless properly disposed of when generated. To aid in the process of chip removal and to minimize damage to the workpiece by the chips it is conventional to locate the element so that each one cuts only a portion of the total cutting width. For the same purpose, cutting elements having different cutting widths are used. These alternative methods produce narrower chips than the slots and facilitate chip disposal.
The use of staggered cutting elements and elements of different widths decreases the efficiency of the cutting operation. The use of the characterized elements helps solve the problem of minimizing chip damage and of disposing of the chips when the workpiece is rotated. However when the tool uses cutting inserts, such inserts if characterized require even more substantial clamping than non-characterized inserts because of the additional forces generated when forming the narrower chip. The chip disposal problem is further exacerbated by the necessity of rigorously clamping the insert into the holder to overcome the centrifugal forces generated by the rotational motion. There are many clamping means available for the retention of inserts. Clamping devices take up room and therefore decrease the number of cutting inserts that can be placed around the periphery of the disc. Also the clamping devices require fasteners that limit the narrowness of the disc which is a problem when the tool is used for narrow slotting such as a saw.
The self-retention of inserts in tool holders are shown in the prior art. For example, U.S. Pat. No. 55,423 shows saw teeth positioned in a circular saw without any obstructing holding or clamping means.
The U.S. Pat. No. 3,785,021 shows a tool holder insert with a clamping arrangement wherein the clamp member clamps by spring effect action. In addition self-locking wedge-shaped inserts having chip shaping means have been used before in cut-off tools. However, none of the prior art patents address the problem of an effective secure retention arrangement for characterized elements in rotary slot cutting tools.
Accordingly it is an object of the present invention to provide new and unique rotary slot cutting tools in which the above referred to problems and disadvantages are substantially reduced or overcome.
According to the present invention an improved rotary slot cutting tool arrangement is provided comprising:
a disc shaped tool,
a plurality of cutting elements around the periphery of said tool, and
means on said cutting elements for narrowing the chips as the chips are formed during the cutting of slots on the workpieces.
To maximize the number of cutting elements on the periphery of the tool, a unique characterization of the cutting element causes the chip to coil into tight compact coils, thus occupying only a minimum amount of space on the periphery of the tool.
The rotary tool uses inserts, in a preferred embodiment, that are retained in the holder by the geometrical characteristics of the holder and the insert, thereby obviating the necessity of special clamping means. The holder includes jaw-like seats for the inserts wherein the contour of the seat matches the contour of the tool holder. In addition the seat may include a spring-like detent which is received in a recess formed in the insert whereby when the insert is placed in the tool holder it is locked in place and removed only by a tool designed for that purpose. Thus, there is no clamping means requiring a minimum thickness of the holder or taking up valuable space on the periphery of the tool.
The cutting elements or inserts are characterized to shape the chips such that the width of the chip is less than the width of the cutting edge of the cutting element; the characterization is preferably in the form of ridges located at and forming part of the cutting surface of the cutting element to thereby shape the chip immediately after being sheared by the straight cutting edges of the insert. By shaping the chip while it is most malleable minimum power is used. The stresses on the formed chip cause it to curl and take a tight helical shape.
In addition the cutting surfaces of the cutting inserts are removed and spaced apart from the top clamping surfaces of the cutting inserts by chip guiding surfaces angled from the cutting surfaces.
Recesses are formed on the tool holder between the inserts for receiving the helically shaped chip. The beginning of the recess has the same angular bias as the chip guiding portion of the cutting insert to facilitate the disposal of the chip during the cutting operation.
Further to enable more cutting inserts per unit of circumferential length, slots are provided in the disc-like tool holder to reduce the strains due to the stresses caused by pressing the inserts into the seats on the holders.